Figure 4. The D-Ala esterase activity of DltE contributes to D-alanylation of the cell envelope and is required to sustain Drosophila juvenile growth.

(a) Amount of D-Ala released from whole cells of WT, ∆dltE, and DltE^S128A by alkaline hydrolysis and quantified by HPLC. Mean values were obtained from three independent cultures with two injections for each. Purple asterisks illustrate statistically significant difference with D-Ala release from WT. ***0.0001<p<0.001; **0.001<p<0.01. (b) Larval longitudinal length after inoculation with WT, ∆dltE, and DltE^S128A strains and PBS (for the germ-free [GF] condition). Larvae were collected 6 d after association and measured as described in the ‘Materials and methods’ section. Purple asterisks illustrate statistically significant difference with larval size of WT; ****p<0.0001. Center values in the graph represent means and error bars represent SD. Representative graph from one out of three independent experiments. (c) Time to pupation: day when 50% of pupae emerge during a developmental experiment (D50) for GF eggs associated with strains WT, ∆dltE, and DltE^S128A or PBS (for the GF condition). Center values in the graph represent means. Purple asterisks illustrate statistically significant difference with WT larval size; **0.001<p<0.01; *p<0.05. (d) Abundance of colony-forming units (CFUs) on fly food and larvae at days 3, 5, and 7 after inoculation with WT, ∆dltE, and DltE^S128A. Purple asterisks illustrate statistically significant difference with WT within each day. *p<0.05.

Figure 4—figure supplement 1. The D-Ala esterase activity of DltE is required to sustain Drosophila juvenile growth.

(a) Experimental replicates from Figure 4b: larval longitudinal length after inoculation with WT, ∆dltE, and DltE^S128A strains and PBS (for the germ-free [GF] condition). Larvae were collected 6 d after association and measured as described in the ‘Materials and methods’ section. Purple asterisks illustrate statistically significant difference with larval size of WT; ****p<0.0001. Center values in the graph represent means and error bars represent SD. (b) Experimental replicates from Figure 4c: day when 50% of pupae emerge during a developmental experiment (D50) for GF eggs associated with strains WT, ∆dltE and DltE^S128A or PBS (for the GF condition). Center values in the graph represent means. Purple asterisks illustrate statistically significant difference with WT larval size; **0.001<p<0.01. (d) Experimental replicates from Figure 4d: abundance of colony-forming units (CFUs) on fly food and larvae at days 3, 5, and 7 after inoculation with WT, ∆dltE, and DltE^S128A. Purple asterisks illustrate statistically significant difference with WT within each day. *p<0.05.